Deep Dive
Why was there a need for standardized measurements in the 1700s?
The 1700s saw a chaotic mix of approximately 250,000 different units of measurement in regular use across various commodities, leading to confusion and hindering trade. The lack of a standard measure exacerbated during famines, such as the one in France, where bakers exploited the uncertainty to sell lighter bread, angering the populace.
How was the meter originally defined?
The meter was originally defined as a fraction of the Earth's circumference, specifically one ten-millionth of the distance from the equator to the North Pole through Paris.
What is the significance of the international prototype kilogram?
The international prototype kilogram, a platinum-iridium cylinder, serves as the physical standard for the kilogram. It is housed in a high-security vault in France and is used to calibrate all other kilogram standards worldwide, ensuring global consistency in weight measurements.
Why did the international prototype kilogram lose weight?
The international prototype kilogram lost weight due to unknown reasons, possibly from excessive cleaning or outgassing of hydrogen from the metal. This discrepancy was discovered during ceremonial weighings against its copies, leading to concerns about the stability of the standard.
How did scientists propose to redefine the kilogram?
Scientists proposed redefining the kilogram using a Watt balance, which measures the weight of an object by balancing it with electromagnetic forces. This method would tie the kilogram to fundamental constants of nature, specifically Planck's constant, making the definition more precise and stable.
What is the new definition of the kilogram?
The new definition of the kilogram is based on Planck's constant, set to exactly 6.626069 times 10 to the minus 34 joule seconds. This mathematical definition replaces the physical prototype, ensuring greater accuracy and stability.
What will happen to the international prototype kilogram after the redefinition?
After the redefinition, the international prototype kilogram will likely be retired to a museum, similar to other historical measurement standards, marking the end of its role as the definitive standard for weight.
- Early measurements were based on body parts and local references.
- The lack of standardization caused confusion and issues in trade.
- The French Revolution led to the need for a unified system of measurements.
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